pcv, vacuum, etc...

[ezernut9mm]

i am wondering about how much vacuum i should have at the back of the carb where the pcv valve connects. there is enough there to suck the valve open and then give me a hickey on my thumb from covering it. that does not seem right.
the engine ran different when i took the pcv out of the valve cover and then when i took the pcv off of the hose the engine idled up about an additional 500 rpm.
this seems to be a carb issue and not a pcv valve issue. any ideas? the carb is a reman so i am wondering if it correct for the type of spacer used and is somehow getting more vacuum that it should. this is on a 360 2v.

[Wes]

You should manifold vacuum at the PCV hose. Your engine shouldn't run different when you remove the PCV from the valve cover, but should almost die/die when the PCV is removed from the hose. Check the other valve cover (air inlet side) if the hose or filter are clogged or plugged off. If your carburetor is out of tune or jetting, you could have some of the symptoms you described.

[ezernut9mm]

this was done without the cap on the drivers side so that side was open.
i figured an old engine like this would have some blowby, but never saw any until i pulled the pcv and then i saw some out of the vc hole. but when i pulled the pcv out of the hose the idle went up and i saw blowby out of both vc's.
should i try to reset the idle without the pcv valve in the hose? it is pulling alot of vacuum.

[Wes]

No you should adjust your air fuel mixture and your idle speed with engine warmed up and everything connected, air cleaner included. The vacuum at the PC valve will be as high as your engine produces at idle, 19-21 inches would be a good strong engine. When you rev it up Vacuum should drop some,and when you slam the throttle closed vacuum should go over your idle idle reading @ 25-28 inches. Just make sure fresh filtered air can enter the the crank case, to help the PCV scavenge blow by.

[ezernut9mm]

this engine runs good with everything hooked up. i have just never had one rev so high when the pcv is disconnected.

[Wes]

It should have stalled or dam near, I suspect you have rich air/fuel ratio, so the extra air doesn't lean out the a/f enough to stall the engine. If it is running good and not fouling plugs, I'd leave it.

[ezernut9mm]

i think i am over thinking this. thanks wes. i'll just keep an eye on the plugs.

[willowbilly3]

The pvc valve does have full engine vacuum and if it kept running at all when you pulle off the hose, 500 rpm rise isn't unusual.
Just pulling the valve from the cover normally wouldn't show much rpm difference but it can. If there are excessive crankcase vapours you might notice a little difference. More likely the hose is stiff and you cocked it a little when you moved it allowing some air to slip by on the connector.